Cracking of hydrocarbon oils



n. 1 1927. Ja 1 c. l.. PARMELEE CRACKING OF HYDROCARBON OILS Filed Oct.8. 1924 Patented Jan. 11, 1927.

' UNITED. STATES 4PATENT O Prier..`

` CHARLES LESTER PABMELEE, F WEST ORANGE, NEW JERSEY, ASSIGNOR TO SIN-GLAIB-REFIENING GOHPANY, OF CHICA-G0, ILLINOIS, A CORPORATION 0F E.

CBACXING OF HYDBOCABBON ILS.

Application med october s, 1924. serial No; 742,347.

invention relates to an, improved pro: ess of cracking hydrocarbons .forthe pr0 duction of lighter hydrocarbon oils, such as `gasoline orpressure distillate,l from heaviery hydrocarbon oils. t

More particularly,"this invention relates to improvements instheoperation of pres sure stills in-'which the bulk ofthe .oil beingv`lation under pressure, considerable amounts of heavy matter, such ascarbon, tar, and the like, are formed. If these heavier materials arepermitted to deposit in or upon the heating surfaces which are incontact with the heating gases or other heating medium, they tend toform a coating thereon which insulates the heating walls from thecooling veffeet of the circulating oil, with the result that the walls,or portions thereof on which the depoition has taken lace, tend tobecome overheatcd; and as t- 1e overheat-ing in-l creases the depositionand that in turn con-- tributes to further overheating, the heatingsurfaces .are apt to be burnt and weakened and sometimes burst unlessthe overheating is noted in time and the still shut down or the firediminished. This de osition of an insulating layer also materia lydiminishes the capacity of the heating surfaces. As cracking continues.'the heavy matters tend to accumulate in the cracking system, and, if theoil is rccirculated through the heating element, the tarry matter andcarbon are again and again aforded opportunity to delosit.y and .lo infact deposit, upon the Walls ofthe heating element, l

In the operation of circulatory cracking stills of the character abovereferred to, the introduction of the hot vapor-laden and vaporizing oilinto the bulk supply tank or vaporizing chamber, as it circulatesl fromthe heating element, tends to cause turbulence or eddying in the bulksupply tank so that the vapors and light cracked constituents are`incompletely liberated in t'he bulk supply tank, and so. that suchvapors and li ht cracked constituents as are' notliberate .are againcarried through the heating element with the circulating oil where theyare. further subjected'to a higher cracking temperature. Thevrecirculation of such lighter constitutents through the heater tends toresult in overcracking, with accompanying increased production of heavytarry matter and light incondensible gases at the expense ofconstituents desirable in the pressure distillate, and also tends toproduce a pressure distillate unsaturated to an objectionable degree.

The present invention includes an improved method of operatingcirculatory pressure stills for cracking hydrocarbon oils in which ,theseparation of heavy matter from the unvaporized oil is promoted beforethe unvaporized oil is recirculated through the.

heating element whereby only relatively clean oil passes through theheating element and deposition of carbon and tarry matter on the wallsof the heating element is lar ely prevented or reduced. The invention aso includes' an improved method of-operatiox1 in which the liberation ofvapors and lightl cracked constituents Afrom the hot oil circulatingfrom the heater is promoted before the unvaporized oil is recirculatedthroughV the heating element whereby overcracking is avoided or reducedand whereby the quan'- tity and quality. of the -pressure distillate maybe improved. The invention also includes an improved method of operationfor preventing or reducing contamination of returned reflux or freshcharging stock in-` troduced during the progress of the crackingoperation with carbon o r tarry matterspreviously produced. Otherfeatures ofthe invention will appear hereinafter.

According to the present invention, the bulk supply tank is arrangedto.' provide a. receivin y vapors rom the heater, in whichcarbon andtarry matter tendsto 'precipitate andi'n which the liberation of vaporsfrom the hot oil is promoted, and a supply.- compartment for leocompartment for the hot oil and y oil circulating to-the -heater towhich un-v `vaporized oil,'relatively free \'from carbon -fandtarry-matterfand fromvapors and light cracked constituents, isovertlowed from the A ,creasing the 'volume of, the heating gases,

ment from time to time.

receiving compartment. Heavy matter may '1 to t-he supply compartment,and may be introduced into direct contact with the vapors in the reuxingoperation and conducted to the supply compartment in admixture with thereflux. Circulation of the oil within the system maybe effected by aforcing means, such as a pump, or by thermosiphonic action. v

The invention will be further described in connection with theaccompanying drawings illustrating two arangements of apparatus adaptedfor the practice of the process of the invention, but it Vwill beundersto'od that the invention is illustrated thereby and not limitedthereto. i

In the accompanying drawings:

Fig. 1 is a diagrammatic view partly in section and partly in elevation'of a still construction adapted for carrying out the invention, and

Fig.,.2 is a fragmentary view of a modifi'ed still lconstruction adaptedfor a modified way 4ofgcarrying out the invention.

,The apparatus shown in Fig. 1 comprises a furnace structure 3 having afire-box 4, a

vertical throat 5, a. heating fine (i, and a stack Hue 7. The heatingflue 6 is provided with baflies 8 and 9, and a battery of tubes 10extends vertically therethrough and is provided with upperv and lowerheaders 11 and 12 respectively. A connection 13 is provided forreturning a. portion of the cooled products of combustion to fluesunderneath the fire-box 4 and at the base of the throat i5 whereby thefresh h ot products of combustion from the burners 15 are somewhatdiluted by the cooler products ofcombustion,

thus diminishing the temperature and inavoiding overheating ofithe fronttubes in the first pass, more evenly and efficiently heating the tubesthroughout,l and protecting the walls of the fire-box and furnacestructure. The tank or drum17 is a relatively long closed cylinderarranged with its long axis vertical and with its upper end extendingwell abovelthe heating element in the furnace. The 4tank isdivided by avertical partition 18 which extends from the' bottom thereof to a levelsubstantially above the top of the heating element 1() dividing thelower portion of the tank 17 into a receiving or separating chamber'19and an exhaust or supply 'chamber 20. The receiving compartment 19 isconnected to the top manifold 21 of the top header 11 by a suitablereturn flow pipe Q2. The supply compartment is connected to the manifold23 of the lower header 1Q. by a circulating line, which, as shown inFig. 1, includes thc horizontal pipe 24, vertical pipe 25, pump Q6,vertical pipe 27 and horizontal pipe In one way of carrying out theinvention. the pump 26 may be dispensed with, and the pipe 24 directlyconnected with pipe Q8 by a pipe 25 as shown` in Fig. 2. The tank andpipe connections may with advantage be heat insulated. A tar lineprovided with a valve 31, extends substantially to the bottom ot `thereceiving chamber 19. A. manhole 32 is provided for cleaning out thecompartment 19 when required. The pipe 313 having a valve 34 isconnected to the lowest point of the bottom of compartment 19 forcharging the still with oil in starting up and pumping out when theoperation is discontinued, and a valved branch 35 therefrom connects toa T 36 between pipes 27 and 28 for withdrawing oll from these pipesbetween runs.

The upper end of the tank above the compartments 19 and 20 may, however,with advantage, be constructed of such volume and suitably equipped toconstitute a reflux tower, and a separate tower dispensed with. Theupper portion of the tank 17 is illustrated as provided with baffles 38which may be of the type commonly employed in reflux towers. The vaporline 39 leadin'g to the condenser is connected directly to the upper endof the tank. The lowermost baffle 38 is-'so disposed as to discharge anyliquid thereon into the supply compartment Q0. A valved line 40 andasprayhead 41 are provided for the introduction of fresh charging stockinto the upper endof the reflux tower, and this feedv mayor may not besupplemented by the introduction of oil through valved connection 47.The vapor line '39. condenser '42 and receiving drum 4?), with its gasrelease line 44 and distillate drawott 45, may be of the type commonlyemployed in connection with cracking stills. A pressure regulating valve46 in line 39 between the reiiux tower and the condenser may be employedfor controlling and reducing the 1 'L 19, either by means of a pump 26or bv thermosiphonic action, the vaporized oil collecting in the upperportion of the tank 17 and being subjected to reflux condensationtherein, thev resulting vapors passing ing element 10 or through bothconnections.

Reflux condensate, and admixed with any feed oil introduced throughconnection Ll is returned to the heating element through compartment 20.The pressure within the cracking system may be'controlled by valve L16or by control of the withdrawal of liquid distillate and uncondensedgases from'the receiver 13. Condensation may -be effected at atmosphericpressure, or at some predetermined intermediate pressure aboveatmospheric pressure.

The bulk of the oil being treated is contained in the tank 1T locatedaway from the furnace 3 and is heated by circulating a stream of oiltherefrom through the .heating element in the furnace and back to thetank. This circulating stream of oil is continuously-withdrawn from thesupply chamber and flows through the described pipe connections to theheating element 10 in the furnace and thence through the upper returnpipe 22 tothe receiving or separating chamber 19. The circulation isadvantageously etfected by, means of a pump 26, rapid circulationincreasing the capacity of' the still and being more elticient inkeeping the heating tubes swept -clean of deposits of carbon and tarrymatter. Under proper conditions, however, the thermal effect in IGo 'ing tubes.

The volume of oilmaintained in the sys-- `tem during normal operation issuch asto keepthe separating chamber 19 illed to the top thereof andoverlowing into the supply chamber 20. and to keep sullicient oil in thesupply chamber 20 to properly maintain the circulation. Where acirculating pump is employed. the level of oil in the supply chamber 20is advantageously maintained considerably below that in the receivingchamber 19. as shown in Fig. 1, so that the oil flowing from compartment19 to compartment 20 passes in a thin sheet or film-down the partition18 which is heated by the oil in the receiving chamber 19. lThis methodof operation promotes the release of gas and yapors from the oil lowingdownwardly over the partition. vhere pump or forced posit.

circulation is employed, the exact level of the oil in compartment 20 isnot important provided it is sufficient to maintain proper circulation,but where thermal circulation is employed, the level of the oil incompartment 20 should be sufficient to maintain circulation, and is ingeneral somewhat higher more closely approaching the 'oil' level incompartment 19. lVhere thermosi phonic circulation is employed. thelevel, of the cooler oil in compartment 20must be such as toovei'balance the column of hotter oil in the heating element 10 and incompartment 19. The decreased density of the hotter eiland the formationof Oases and vapors in heatingeleme'nt 1() antl the discharge of thesegases and vapors in that portfon o compartment 19 above the level ofreturn pipe*22 tends to maintain circulation, but withtherinalcirculation` the level Y.in compartment 20 must be higher than with`pump circulation and usually' must be maintained above the level ofreturn pipe 22.

The oil from the return.'pipe 22 is discharged into the chamber 19 below'the level of the oil therein but at a considerable distance above thebottom of the chamber. The upward movement of oil in the chamber 19 isrelatively' slow, due to the relatively large cross section of thecolumn of oil in this chamber as compared to that of the oil` streamentering it, thus aiording a very fa vorable condition for theseparation of any vcarbon or tarry matter formed in the passage of theoil through the heating tubes 1() or the pipe 22. That portionof thechamber 19 below the connection ofpipe 22 theretcl offers aY quiescentzone in which the carbon and heavier tarry products separating from thecirculating oil may settle out and de- The heavier products depositingin chamber 17 may be drawn ol intermittently or continuously during theoperation of the still through the tar line 30. The oilyenteringI thechamber 19 is thus substantially freed of the' heavy matter vformedduring the 4cracking operation and only relatively clean or clarifiedoiloverflows into the sup.

lll() ply chamber 20. Thus, though continuous recirculation ofunvaporized oil is maintained through the heating element, the

heaviest of the products formed are not returned to the heating elementso that the tendency to deposition of tar and carbon is minimized l19and 20 and on the bam above the oil level in chamber 20 are free and inunoblit) structed communication with the vaporizing and reuxing spacepermitting a ready release of vapors and gases formed. By maintainingthe level of the liquid in the chamber 19 above the heating element and4the connections thereto, there is no opportunity for the formation ofvapor pockets and the heating tubes and connections are kept full of oilthroughout the operation. Reflux is deflected by the lowermost baffle 38into the chamber 20, so that the' tar and carbon -free reflux isreturned to the cracking operation without admixture with the hot oilcontaining heavy matter.

Fresh charging ,tock, likewise, is advantageously introduced into thestill system subsequently to the separation of tar and carbon from therecirculated unvaporized oil. The fresh oil may be introduced throughconnection 47 into the clarified oil flowing from compartment throughpipe 24, or it may be introduced through connection at the upper end ofthe tank 17, or through both of these connections. Where the fresh oilis introduced at the upper end of the reflux tower in the tcp of thetank 17, it assists in the reflux condensation vand affords a convenientcontrol of the still head temperature. The unvaporized fresh oilintroduced through connection 40, in' admixture with any reflux formedin the upper end of the -drum 17, is directed into .compartment 20 bythe lowerinost baille 38 without admixture with the unclarified oil inAcompartment The method of the present invention is of special value andapplication in connection with continuous or semi-continuous methods ofoperation in which fresh `charging stock is introduced during theprogress of the' cracking operation and in which tar is withdrawn tomaintain the concentration of tarry constituents in the charge below anobjectionable point. In carrying out the present invention in connectionwith such processes,

the tar is withdrawn as it is separated by precipitation from thecirculating oil. For example, in the apparatus illustrated, tar may bewithdrawn from the lower part of compartment 19, Where the tarryconstituents tend to concentrate, in amount sufficient to prevent orretard increase in concentration of such constituents in the circulatingcharge during the course of the cracking operation.

It will thus be seen that this invention pro? vides an improved methodof operating circulatory pressure stills which is of particularadvantage in prolonging the cracking operation by promoting theseparation of carbon and tarry constituents from the circulating oil andby recirculating only a relatively clean or a clarified oil. The processof the invention also offers advantages in eliminating or reducingovercracking and the further decomposition of constituents desirableseparating chamber, subjecting the oil to a cracking temperature in theheating element and maintaining the oil in the separating chamber andthat in the supply chamber in indirect heat exchanging relation,effecting a separation of carbon and tarry matter in the separatingchamber and withdrawing the separated carbon and tarry matter, passingthe clarified liquid oil to the supply chamber, collecting the vaporsliberated in the separating chamber and the supply chamber andsubjecting them to a refluxing operation, in-

troducing fresh oil into the rellu'xin opera.

tion and passing the admixed re ux and fresh oil from the refluxingoperation to the l supply chamber.

2. A process of cracking hydrocarbon oils which comprises circulatingoil from a supply chamber through a heating element to a separatingchamber, subjecting the oil to af cracking temperature in the heatingelement and maintaining the oil in the Separating chamber and that inthe supply chamber in indirect heat exchanging relation, effecting aseparation of carbon-and tarry matter in the separating chamber andwithdrawing the separated carbon and tarry matter, passing the clarifiedliquid oil to the .supply chamber, collecting and removing the vaporsliberated in the separating chamber and supply chamber and introducingfresh oil to the supply chamber. A

3. A process of cracking hydrocarbon oils which comprises introducingfresh oil to a supply chamber, circulating oil from the supply chamberthrough a heating element to a separating chamber, subjecting the oil toa cracking temperature in the heating element and maintaining the oil inthe sepa# rating chamber and that inv the supply chamber in indirectheat exchanging relation, effecting a separation of carbon and tarrymatter in the separating chamber and withdrawing the scparated'carbonand tarry mattei', passing the. clarified liquid oil to the supplychamber, collecting the vapors liberated in the separating `chamber andsupply chamber and subjecting them to a refluxing operation, andreturning thereflux to the supply chamber. l

4. A process of cracking hydrocarbon oils which comprisescirculating oilfrom a supply chamber through a heating element t0 mixed reflux andfresh oil to the supply.

chamber. e

5. A process of cracking hydrocarbon oils which comprises circulatingoil from a supplychamber through a heating element to a separatingchamber, subjecting the oil to a cracking temperature in the heatingele,- ment and maintaining the oil in the sepa rat-ing chamber and thatin the supply chamber in indirect heat exchanging relation, effecting aseparation of carbon and tarry matter in the separating chamber andwithdrawing the separated carbon and tarry' matter, passing theclarified liquid oil to the supply chamber, collecting the vaporsliberated in' the separating chamber and the supply chamber andsubjecting them -to a refiuxing operation, and returning the refiux ltothe supply chamber.

6. A process of cracking hydrocarbon oils which comprises circulatingoil from a supply chamber through a heating element to a separatingchamber, subjecting the oil to a cracking temperature in the heatingele-` ment, effecting a separation `of carbon and tarry matter in theseparating chamber and withdrawing the separated carbon and tarrymatter, passing the clarified liquid oil to the supply chamber inindirect heat exchanging relation with the oil from the heating ele.-

. ment in the separating chamber, collecting the vapors liberated in theseparating chamber and the supply chamber and subjecting them to arefluxing operation and returning the refiuxto the supply chamber.

7 A process of cracking hydrocarbon oils which comprises circulating oilfrom a supply chamber through a heating element toga separating chamber,subjecting the oil toa cracking temperature in the heatlng I element,eii'ecting a separation of carbon and tarry matter in the separatingchamber and withdrawing the separatedcarbon and tarry matter, collectingand removing the vapors liberated, and passing the clarified 'liquid oilto the supply chamber in indirect heat exchanging relation with the oilfrom the heating element in the separating chamber.

8. A process of cracking hydrocarbon oils which 'comprises circulatingoi1from a supply chamber through a heating elementtoa separatingchamber, subjecting the oil to a cracking temperature in theheatingelement. 'effecting a separation of carbon and tarry matter in theseparating chamber, collecting and removing the vapors liberated, andpasing the clarified liquid oil to the supply chamber in a relativelythin film from [which vapors are readily liberated.

9. A process of cracking hydrocarbon oils which comprises circulatingoil from a supply chamber through a heating element to a separatingchamber, subjecting the oil to a cracking temperatureV in the heatingelement, effecting a separation of carbon and tarry matter in theseparating chamber and withdrawing the separated carbon and tarrymatter, collecting and removing the vapors liberated, passing theclarified liquid oil to' the supply chamber in indirect heat exchaningrelation with the oil from the heating elementin the separating chamber,and introducing fresh oil to the supply chamber.

10. .A process of cracking hydrocarbon oils which' comprises circulatingoil from a supply chamber through a heating element to a separatingchamber, lsubject-ing the oil to a cracking temperature in the heatingelement, effecting a separation of carbon and tarry matter in theseparating chamber, passing the clarified'liquidoil to the supplychamber in arelatively thin film in indirect heat exchanging relationwith the oil from the heating element in the separating chamber, andcollecting and removing the `vapors liberated.

11. A process of cracking hydrocarbons which comprises circulating oilthrougha heating element, subjecting it to av crack- 111g heated oilinto a vertically disposed receptacle below the normal liquid level onone side of a partition dividing the lower part` clarified oil to theheating element, and collecting and removing the vaporized oil the upperpart of the receptacle.

12. A process of cracking 'hydrocarbons from temperature therein,introducing -the which comprises mechanically circulating oilA through aheating element, subjecting it to a cracking temperature therein,introducing the heated oil into a vertically disposed receptacle belowthe normal liquid level on one side of a partition dividing the lowerpart of the receptacle, effecting a separation of carbon and tarrymatter in the body ofoil on the same side of partition, maintaining alower liquid level on the other side of the partition and overfiowing.the clarified liquid oil across the partition and .returning theclarified oil to the heating'element, and coltemperature therein,introducing the heated oil into a vertically disposed receptacle belowthe normal liquid level on one side of a partition dividing the lowerpart of the receptacle, effecting a separation of carbon and tarrymatter in the,b`6dy of oil on the same side of partition, maintaining alower i liquid level on the other side of the partition and overflowingthe` clarified liquid oil across the partition, subjecting the vaporizedoil to a refluxing operation in the upper part ofv the receptacle,directing lthe reiux condensate to the compartment with tllc overflowingoil in the lowerpart of the receptacle, and recirculating the oiltherein through the heating element.' l

14. A process of cracking hydrocarbon oils which comprises circulatingoil through a heatingviielement, subjecting it to a cracking temperaturetherein, introducing the heated Yoil into a vertically disposedreceptacle below the normal liquid ylevel on one sideof a partitiondividing the lower'part of the receptacie, effecting a separation ofcarbon and mixed reflux to .thc/compartment in theflow'- er part of thereceptacle with the overflowing oil, and recircnlating theoil in thislatter. compartment through the heating Velement. i

v In testimony whereof I aiix my slgnature.

CHARLES ,LESTER PARMELEE; l

